A research team at the U.S. Department of Energy’s SLAC National Accelerator Laboratory had just discovered a new method of fabricating a nickel oxide material. The reported newly synthesized substance was able to demonstrate clear properties of superconductivity.
Superconductivity, in simplest terms, is the ability of an object or material to transmit electric current with zero loss of efficiency. At the moment, this is only achievable when materials are subjected to very cold temperatures, as the very nature of electrons moving through a material by itself creates heat, thus loss of efficiency, even at the micro-scale.
Which is why the concept of achieving superconductivity at higher temperatures has been a Holy Grail of sorts to the researchers in this field. Cuprate superconductors were the first step to this long winding road, as it was discovered in 1986 that high-superconductivity was relatively possible for the material. A cuprate material primarily consists of copper oxides, that are given microscopic spacer layers, and are combined with another metal (either lanthanum or yttrium) to increase the temperature limit for its superconductivity.
Before, it was thought that superconductivity beyond 30 Kelvin (-243 °C) was impossible. Thanks to cuprate materials, and other subsequently discovered superconductive compounds afterward such as hydrogen sulfide, the upper (practical) limit has now been extended to 80 Kelvin (-193 °C).
Nickel has long been thought of as potentially superconductive at higher temperatures as well, being right beside copper in the periodic table. However, a method that can efficiently produce nickel oxides for such applications has eluded researchers for decades.
The recent report, however, stated that the researchers were able to create the material through several technical steps. First, the perovskite material is “doped” with strontium. Next, it was exposed to another material that forced out its oxygen atoms on a single outer layer. After that, it was just a matter of very, very carefully realigning and pulling out the oxygen atoms to form the nickel oxide material.
As lead researcher Danfeng Li explains it, “When you play Jenga games, you need to be very careful in pulling these blocks. We also used a very gentle way, which we call it soft chemisty. That is a process that allows us to take oxygen blocks out.”
Testing of the fabricated material confirms that it does function as a superconductor. The catch, however, is that at the moment, it can only operate at a maximum of 15 Kelvin (-258 °C), way lower than some of the industrial-grade superconductive materials commonly used today.
Scientists working on the material do admit that the research is still at its very, very early stages, and that more data will still be needed. This is, after all, the very first time that a nickel oxide material was fabricated using the aforementioned method. There are still, in their own words, a “whole battery of investigations that are still going on with cuprates” that the nickelate needs to be subjected to as well.
The next plan is to dope the perovskite material using different methods. This is to observe whether it would significantly change the properties of the resulting nickelate material, and hopefully, to further increase its effective operating temperature.